Rain changes the mood on Saturday at Isthmus Jazz Festival 2009

Rain displaced the Isthmus Jazz Festival to the cramped confines of the UW Memorial Union Rathskeller on Saturday. That changed the vibe of the night. No sweeping sunset. No shimmering lake. No girls in their summer clothes taking in the twilight.

Inside the Rathskeller the sound of a nine-piece jazz ensemble confronts your personal space in a way it never could on the Terrace. There was no steady hum of small talk accompanying the Tim Whalen Nonet. If you tried to share words with your neighbor or date, they'd likely not hear you over the sound of three saxophones, a trombone, two trumpets, a drum set, bass and keyboard.

Listening was the order of the night.

The sheer size of Whalen's ensemble creates more call-and-response options than most jazz bands would know what to do with.

The Nonet makes Whalen's keys the centerpiece. The arrangements frequently incorporate the orchestral force of a six-piece horn section. Sometimes, that section gives way to an intimate trio that thrives on direct interplay of piano, drums and bass.

I've seen the Nonet at past jazz festivals and am always struck by how much Nick Moran contributes to the group's stage presence. Generally speaking, I find jazz performers to be less charismatic than their rock counterparts (yeah, all that improvisation demands technical attention, whereas the rockers can concentrate on being showy). But Moran is an exception. Standing by his upright bass, he exudes energy and looks like there's no place he'd rather be.

I can't say the same for much of the Nonet's horn section. During their silent parts, they looked vacant, if not bored.

Whalen's keyboard dexterity was precise in its flight of madness on "Café Gitmo."

Just before 8 o'clock, I headed down to the Wisconsin Union Theater for the evening's headlining event, the David Sánchez Quartet. I noticed the absence of the old arcade lights across the hall from the Rathskeller. Maybe it was the beer, but I felt a wave of nostalgia for the campus area's past.

I recalled the tacky International House of Pancakes that used to mark the bend where Gorham turn into West Johnson, back in the days before students moved into luxury high-rises. I remembered the Mango Grill, huddled in the back corner of the old University Square.

I suppose I was having a private jazz interlude of my own in the horn section of my mind.

Fortunately, the walk to the Union Theater was short, and the also-intoxicating effect of David Sánchez beckoned.

The quartet was one of the most singular jazz groups I have ever seen. The mix of Lage Lund's guitar, Sánchez's sax, Henry Cole's drums and Orlando Le Fleming's bass was deeply rich in subdued emotion.

The set list included pieces from the latest Sánchez album, Cultural Survival. Sánchez has described the recording as a sonic rumination on society, culture and injustice.

That was clear as Sánchez introduced "The Forgotten Ones" and referenced the fate of New Orleans residents during Hurricane Katrina as an inspiration.

The technical command of these four musicians was striking. Lund's guitar was warm and articulate. Cole's drums were restrained without sacrificing feeling. Le Fleming's steady bass grounded the quartet.

Between their parts, Sánchez stepped forward to steal the show. With his eyes closed in deep concentration, he made the kind of tonally balanced and plush sounds that have distinguished him from his tenor sax peers.

The music's vibe was somber, and it suddenly felt completely right that the evening was way too cool, cloudy and wet for a summer festival.

Sánchez showed the audience that the elements of jazz are most vital when they're unpredictable, and Mother Nature seemed to agree.